SOLUTION: TWO PERSONS R AND S HAD TO MEET AT A PLACE 36KM FROM WHERE TEY WERE AT THAT MOMENT. S,WHO WAS GIVEN A HEAD START OF 2HOURS, REACHED THE DESTINATION 12MIN EARLIER THAN R. IF R TRAVE

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Question 512888: TWO PERSONS R AND S HAD TO MEET AT A PLACE 36KM FROM WHERE TEY WERE AT THAT MOMENT. S,WHO WAS GIVEN A HEAD START OF 2HOURS, REACHED THE DESTINATION 12MIN EARLIER THAN R. IF R TRAVELED 18KMPH FASTER THAN S, AT WHAT SPEED DID R TRAVEL?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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TWO PERSONS R AND S HAD TO MEET AT A PLACE 36KM FROM WHERE THEY WERE AT THAT MOMENT.
S, WHO WAS GIVEN A HEAD START OF 2HOURS, REACHED THE DESTINATION 12 MIN EARLIER THAN R.
IF R TRAVELED 18KMPH FASTER THAN S, AT WHAT SPEED DID R TRAVEL?
:
Change 12 min: 12/60 = .2 hrs
:
Let r = R's speed
then
(r-18) = S's speed
:
Write time equation
r's time + .2 hrs = s's time - 2 hrs
36%2Fr + .2 = 36%2F%28%28r-18%29%29 - 2
36%2Fr = 36%2F%28%28r-18%29%29 - 2 -.2
36%2Fr = 36%2F%28%28r-18%29%29 - 2.2
multiply both sides by r(r-18), resulting in
36(r-18) = 36r - 2.2r(r-18)
36r - 648 = 36r - 2.2r^2 + 39.6r
36r's cancel write a quadratic equation
2.2r^2 - 39.6r - 648 = 0
Use the quadratic formula: a=2.2, b=-39.6, c=-648
the positive solution: r = 28.38 km/hr